I'm gradually getting my boat cleaned up after having lived on her since the end of April. A lot of cooking was done on board by a lot of different people, and I shudder to think what the grey water tank looks like. It will need to be cleaned out, which is simply the second most disgusting job on board.

Is there some other, less disgusting way to do it? Put hot water and dishwasher tabs down it? Pour Coca Cola down it? Some enzyme to break up and disperse the filthy, horrible, stinky deposits which build up in it? Anything at all, other than cleaning it out by hand???? I start to gag just thinking about doing this horrible job.

Just a question. Why ever are you storing grey water on the boat? When I bought Idora she had a grey water tank that was disgusting. Clean it out? Oh heck no! Rip it out. I built a collection manifold with a mini float switch to activate a whale pump. No sooner does grey water get to the manifold then its being pumped overboard. No storing of nasty semi sewage from the sink(s). No smell, no cleanup, no problems. Just sayin.

__________________- Never test how deep the water is with both feet -
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I don't know about that! Wouldn't that just whip the sludge up and disperse it into the air, creating a huge stench? And leave me with a stinky vacuum cleaner on top of everything else?

Try with a bucket of clean water see what happens. You will feel confident with the technique/equipment then.

I have used wet&dry vacuum cleaners to suck dry bilges, tanks and other such hard to access places. Very easy and almost mess free. Sure, afterwards you may have to clean the tank of the vacuum cleaner.

BTW if yours has any filter in line (often in the form of a fine mesh or foam) remove this for the dirty job.

Try with a bucket of clean water see what happens. You will feel confident with the technique/equipment then.

I have used wet&dry vacuum cleaners to suck dry bilges, tanks and other such hard to access places. Very easy and almost mess free. Sure, afterwards you may have to clean the tank of the vacuum cleaner.

BTW if yours has any filter in line (often in the form of a fine mesh or foam) remove this for the dirty job.

Cheers,
b.

He's right. Get a long hose for the wet/dry shop vac, leave it on deck and run the hose down a hatch. Vacume your troubles away. Then just dump the vac and your done. It really works.

Once I used Simple Green and water mix to clean my bilges. I set about vacuuming it out when the vac signaled it was full by shutting off. When I turned around I saw the cabin wall behind me covered with foam, where it had blown out the vac exhaust. Note to self - don't do this again.

Don't know about gray water, but when I clean my black water tank I just get it pumped out, then use powered cleaner and a long brush to scrub the interior. This way I can inspect the level through the white side wall.

I have never had to tackle this problem, but I would suggest emptying the grey water tank before your next channel crossing, pouring in a couple of packets of bicarbonate of soda and a few litres of vinegar (both dirt cheap, effective and non damaging) and letting it slosh around for 10 hours. On the way back repeat with hot water and a pack of bicarb.

__________________"The cure for anything is salt water: sweat, tears or the sea." Isak Dinesen"To me the simple act of tying a knot is an adventure in unlimited space." Clifford Ashley

I've had an RV for years, they ALL have grey water tanks.
First if you have access the shop vac will work much better than you think, I used one to pump the porti potti we had one last boat as there was no pump out available.
RV stores sell chemicals to keep the grey water tank from smelling and keep it clean, but the best answer is dilution, lots of water and no food. Is it like an RV to where the shower water goes into it also?
If it's a metal tank, I would be a little leery of chemicals

I've had an RV for years, they ALL have grey water tanks.
First if you have access the shop vac will work much better than you think, I used one to pump the porti potti we had one last boat as there was no pump out available.
RV stores sell chemicals to keep the grey water tank from smelling and keep it clean, but the best answer is dilution, lots of water and no food. Is it like an RV to where the shower water goes into it also?
If it's a metal tank, I would be a little leery of chemicals

Thanks to everyone for enlightening me about shop vacs. I don't have one on board, but will now consider this. How would they deal with oily water in the enginebilge? That's another problem spot on my boat. That would be a really good excuse for buying another appliance (and more importantly, finding a place to store it), if it would deal with that problem as well.

And that's a hot tip about RV stores. Yes, my boat has two plastic grey water tanks which take all grey water, including sink, shower, and washing machine discharge, and pump it overboard via Whale Gulper 220 pumps.

I try to keep food out of it, but when you're feeding up to five people at a time and washing pots, pans, and dishes after them, and if all kinds of different people are doing the washing up, it is really just impossible. Food is going to get down the drain no matter what you do, to rot and stink in the grey water tank. It's vented to the outside, so it doesnt bother anyone if it's not opened up, but open it or take a hose off and watch out! It's absolutely horrible.

Shop vacs will suck most anything that will fit in the hose. Be sure to remove the filter before you suck up any liquid and be darn sure no liquid that could possibly burn is ever sucked up. I assume the arc from the electric motor could cause an explosion.
Why not delete the grey water tanks, are they required where you are?

Any reason why you can't use a marina pumpout facility to empty the tank? Once you have it emptied, you can flush and rinse it out with detergent and water.

I could, but since it only holds 20 liters or so, that's a bit of overkill. Once I've opened up the tank to empty it, the stench is out in any case. I normally bail it out into a bucket and chuck it overboard -- bleh! Then wash it out. It's absolutely disgusting.